The present invention generally relates to reproducing apparatuses for reproducing recorded signals from a rotary recording medium, and more particularly to a reproducing apparatus which can selectively and satisfactorily carry out a still-picture reproduction and a normal reproduction, and also accurately carry out a normal reproduction even when there is a signal dropout in the signal which is reproduced from the rotary recording medium during the normal reproduction.
An information signal recording and reproducing system has been previously proposed in which the recording system forms pits in accordance with the information signal to record the information signal along a spiral track on a flat rotary recording medium (hereinafter simply referred to as a disc), without forming a groove therein. In the reproducing system, a reproducing stylus scans over this track to reproduce the recorded information signal in response to variations in the electrostatic capacitance formed between the reproducing stylus and the disc.
In this previously proposed system, since no grooves are provided on the disc for guiding the reproducing stylus, it becomes necessary to record, on the disc, pilot or reference signals on or in the vicinity of a track of the information signal such as a video signal. Upon reproduction, the reference signals are reproduced together with the video signal. Tracking control is carried out so that the reproducing stylus accurately scans over the track in response to the reproduced reference signals.
By use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged, since the recording track has no groove. The reproducing stylus can repeatedly scan over the same portion of the track many times, whereby it becomes possible to carry out a special reproduction such as still-picture reproduction, slow-motion reproduction, or quick-motion reproduction.
In the above type of a disc, a standard is set for the above proposed system so that four fields of the video signal are recorded for one track turn of the disc. This standard was set in order to increase the recording capacity under the restrictions which are introduced due to the practical diameter and rotational speed of the disc, the relative linear speed between the reproducing stylus and the disc for obtaining a satisfactory signal-to-noise (S/N) ratio, and the like.
When a still-picture reproduction is carried out with the above disc, the same track turn is reproduced repeatedly. Accordingly, the four fields of the video signal are repeatedly reproduced in this case, to carry out the still-picture reproduction. However, if the picture content of the video signal which is to be reproduced is a moving picture, the picture which is recorded in one track turn becomes different in each of the four fields. As a result, the picture obtained by the above still-picture reproduction is not completely still, and the picture appears to undergo a reciprocating movement. Hence, as the movement in the above moving picture becomes faster, the reciprocating movement in the reproduced still picture increases in magnitude. Therefore, there is a disadvantage in that the reproduced still picture does not appear still, and is unpleasant to watch.
On the other hand, another system may be considered wherein the same video information content is repeatedly recorded in four fields in one track turn, and the still- picture reproduction is carried out by repeatedly reproducing the same one track turn. In this case, even if the same one track turn is repeatedly reproduced, the reproduced still picture is completely still, because only the same video information content is repeatedly reproduced from the four fields which make up the above one track turn.
If the above disc is repeatedly recorded with the video information of the first field throughout the four fields in the first track turn, repeatedly recorded with the video information of the fifth field throughout the four fields in the succeeding track turn, and thereafter similarly and repeatedly recorded with the same video information throughout the four fields in one track turn, the reproduced still picture is completely still. However, because 3/4 of the video information is missing, there is a disadvantage in that the movement in the reproduced picture is not smooth and continuous upon normal reproduction.
On the other hand, the disc may be repeatedly recorded with the video information of the first field throughout the four fields in the first track turn, repeatedly recorded with the video information of the second field throughout the four fields in the succeeding track turn, and thereafter similarly and repeatedly recorded with video information of each field throughout the four fields in one track turn without missing any video information. When playing such a disc, a completely still reproduced picture can be obtained. However, upon normal reproduction, the video information in each field is reproduced four times, and the reproduced picture becomes a slow-motion reproduction picture. Moreover, in discs capable of providing completely still reproduced picture, there is a disadvantage in that an audio signal cannot be reproduced in a normal manner.
In order to overcome the above described problems, a disc and reproducing apparatus therefor was proposed in a U.S. patent application Ser. No. 363,795, Pat. No. 4,490,752, filed March 31, 1982 entitled "ROTARY RECORDING MEDIUM AND REPRODUCING APPARATUS THEREFOR" in which the assignee is the same as the assignee of the present application. In this proposed disc and reproducing apparatus, the disc is repeatedly recorded with a video signal of the same unit for a plurality of field periods in each track turn, and divided audio signal parts which are obtained by dividing an audio signal in units of field periods of the video signal which is to be reproduced are successively arranged and recorded on a recording track of the video signal according to a scanning locus of a reproducing element on the disc upon normal reproduction during which change of track is performed by forcibly shifting the reproducing element at least once or a plurality of times for two revolution periods of the disc. Thus, the disc reproducing apparatus can obtain a completely still reproduced picture by repeatedly reproducing the video signal of the same unit in one track turn upon still-picture reproduction. Upon normal reproduction, a satisfactory normal reproduction picture and a normally reproduced audio signal can be obtained, by forcibly shifting the reproducing element to another track at predetermined positions on the disc.
However, during the normal reproduction, the reproducing element may be forcibly shifted to another track at position other than the original intended shifting position. In such a case, the normal reproduction picture and the normally reproduced audio signal which are obtained, are unsatisfactory. Furthermore, the video signal which is recorded on one recording surface of the disc, is usually not from the same kind of a video signal source. That is, a video signal from one kind of a video signal source is often mixed into the video signal from another video signal source. For example, when recording an educational program, the picture corresponding to a scene in which a teacher and the like comments, is obtained from a video signal which is reproduced from a magnetic recording and reproducing apparatus. On the other hand, the picture corresponding to a scene in which the teacher's comments are finished and the contents are described concretely, is obtained from a video signal from a movie film, for example.
In this case, the recording method for the video signal which is reproduced under the normal reproduction, differs according to the video signal source. Hence, it becomes necessary to change the scanning locus of the reproducing element according to the kind of the video signal source. However, it is difficult to cause the reproducing element to scan over a predetermined scanning locus upon normal reproduction in accordance with the video signal source, without specific information thereof.
The disc may be recorded with a video information on one recording surface, where the video information is time-sequentially multiplexed with two different video information. One video information may be a video information which is to be reproduced with a picture arbitrarily selected from a still picture and a normal reproduction picture, and the other video information may be a video information which is to be reproduced only as a normal reproduction picture. For example, in a program containing a golf tournament, the picture corresponding to the scene in which the player makes a shot is a video information which can either be obtained as a still picture or a normal reproduction picture, and this scene is selectively reproduced as a still picture or a normal reproduction picture. On the other hand, the picture corresponding to a scene in which the player walks to his golf ball need not be reproduced as a still picture, and thus, this scene is a video information which is to be obtained only as a normal reproduction picture. When playing such a disc, it is highly desirable to obtain a normal reproduction picture in which the movements are natural. This may be realized if the reproducing apparatus can automatically discriminate the tracks which are recorded with the video information which is to be obtained as either one of the selected still picture and the normal reproduction picture, and the tracks which are recorded with the video information which is to be obtained only as the normal reproduction picture.
In addition, in the case of the slow-motion reproduction, the video information which is recorded on one track turn is repeatedly reproduced for a number of times in accordance with the slow-motion reproduction ratio, the video information which is recorded on one succeeding track turn is repeatedly reproduced for the same number of times, and these reproducing operations are successively performed. Hence, the same disadvantages which are introduced in the case of the still-picture reproduction described before, are introduced during the slow-motion reproduction. Further, in the conventional disc and the above proposed disc, the video information (sports program and science experiment program, for example) which is to be reproduced in slow-motion, is recorded throughout a plurality of track turns by a normal recording. Accordingly, the recording method is uneconomical because there is a limit to the recording area of the disc.
Moreover, in a case where the video information which is to be reproduced by the normal reproduction and/or the video information which is to be reproduced by the still-picture reproduction, and the video information which is to be reproduced by the slow-motion reproduction, are respectively time-sequentially recorded on the same recording surface of the disc, it will be useful if the reproducing apparatus can automatically discriminate the reproduction mode of the video information which is recorded on the track which is being reproduced.
In order to eliminate the various problems described heretofore, a rotary recording medium and a reproducing apparatus therefor were proposed in a U.S. patent application Ser. No. 433,872 filed October 13, 1982 entitled "ROTARY RECORDING MEDIUM AND REPRODUCING APPARATUS THEREFOR" in which the assignee is the same as the assignee of the present application.
According to this proposed disc, the disc comprises a video signal of the same unit repeatedly recorded for N-field period (N is a natural number greater than or equal to 2) for each track turn, a track shift address signal for instructing the existence of forced track shift of a pickup reproducing element, the shifting direction, and the shifting position, recorded on at least one position for one revolution of the disc with a constant period regardless of the kind of video signal source of the video signal, where the track shift address signal comprises at least a synchronizing code, disc type discriminating code, a kick existence instructing code, and a kick direction instructing code, and divided audio signal parts which are obtained by dividing an audio signal for every field period of the video signal which is reproduced. The divided audio signal parts are successively arranged and recorded according to a scanning locus of the pickup reproducing element upon normal reproduction. The disc has track parts which are recorded with the divided audio signal parts on at least one part of a recording surface thereof.
According to the above disc, a completely still reproduced picture, normal reproduction picture, and normally reproduced audio signal can be obtained selectively. In addition, it is possible to obtain a slow-motion reproduction picture of a slow-motion reproduction ratio which is specified by the creator. Moreover, the scanning locus of the pickup reproducing element when obtaining a normal reproduction picture or a slow-motion reproduction picture by forcibly shifting the pickup reproducing element to another track, is uniquely determined. Thus, a normal reproduction picture and normally reproduced audio signal can be obtained accurately, even from a disc in which the still picture recording tracks are scattered on the same recording surface thereof.
However, according to the above reproducing apparatus, the track shift address signal is discriminated during the normal reproduction so as to forcibly shift the pickup reproducing element. Thus, when the track shift address signal is not reproduced due to signal dropout and the like, the pickup reproducing element will not be shifted at predetermined positions on the disc. In this case, because the audio signal is recorded in accordance with the scanning locus of the pickup reproducing element during the normal reproduction, there is a problem in that the reproduced audio signal will be discontinuous. In addition, the movements in the normal reproduction picture will be unnatural in this case, since the pickup reproducing element is not shifted at the predetermined positions on the disc.